The present disclosure is generally directed to establish a dual-roll system which integrates both a delivery member and a cleaning foam member in direct contact with a bias-charge roll (BCR) surface. The present invention increases the effective lifetime of the BCR cleaning system and the delivery member (or liquid materials applicator system). The delivery member may be a delivery roller and the cleaning foam member may be a cleaning foam roller.
In electrophotography or electrophotographic printing, the charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image may be developed by contacting it with a finely divided electrostatically attractable powder known as toner. Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced or printed. The toner image may then be transferred to a substrate or support member (e.g., paper) directly or through the use of an intermediate transfer member, and the image affixed thereto to form a permanent record of the image to be reproduced or printed. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original image or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
The described electrophotographic copying process is well known and is commonly used for light lens copying of an original document. Analogous processes also exist in other electrophotographic printing applications such as, for example, digital laser printing and reproduction where charge is deposited on a charge retentive surface in response to electronically generated or stored images. To charge the surface of a photoreceptor, a contact type charging device has been used, such as disclosed in U.S. Pat. Nos. 4,387,980 and 7,580,655, which are incorporated herein by reference. The contact type charging device, also termed “bias charge roll” (BCR) includes a conductive member which is supplied a voltage from a power source with a D.C. voltage superimposed with an A.C. voltage of no less than twice the level of the D.C. voltage. The charging device contacts the image bearing member (photoreceptor) surface, which is a member to be charged. The outer surface of the image bearing member is charged at the contact area. The contact type charging device charges the image bearing member to a predetermined potential.
Electrophotographic photoreceptors can be provided in a number of forms. For example, the photoreceptors can be a homogeneous layer of a single material, such as vitreous selenium, or it can be a composite layer containing a photoconductive layer and another material. In addition, the photoreceptor can be layered. Multilayered photoreceptors or imaging members have at least two layers, and may include a substrate, a conductive layer, an optional undercoat layer (sometimes referred to as a “charge blocking layer” or “hole blocking layer”), an optional adhesive layer, a photogenerating layer (sometimes referred to as a “charge generation layer,” “charge generating layer,” or “charge generator layer”), a charge transport layer, and an optional overcoating layer in either a flexible belt form or a rigid drum configuration. In the multilayer configuration, the active layers of the photoreceptor are the charge generation layer (CGL) and the charge transport layer (CTL). Enhancement of charge transport across these layers provides better photoreceptor performance. Multilayered flexible photoreceptor members may include an anti-curl layer on the backside of the substrate, opposite to the side of the electrically active layers, to render the desired photoreceptor flatness.
Conventional photoreceptors are disclosed in the following patents, a number of which describe the presence of light scattering particles in the undercoat layers: Yu, U.S. Pat. No. 5,660,961; Yu, U.S. Pat. No. 5,215,839; and Katayama et al., U.S. Pat. No. 5,958,638. The term “photoreceptor” or “photoconductor” is generally used interchangeably with the terms “imaging member.” The term “electrophotographic” includes “electrophotographic” and “xerographic.” The terms “charge transport molecule” are generally used interchangeably with the terms “hole transport molecule.”
To further increase the service life of the photoreceptor, use of overcoat layers has also been implemented to protect photoreceptors and improve performance, such as wear resistance. However, these low wear overcoats are associated with poor image quality due to A-zone deletion (i.e. an image defect occurred in A-zone: 28° C., 85% RH) in a humid environment as the wear rates decrease to a certain level. For example, most organic photoconductor (OPC) materials sets require a certain level of wear rate in order to suppress A-zone deletion, thus limiting the life of a photoreceptor. In addition, high torque associated with low wear overcoats in A-zone also causes severe issues, such as motor failure and cleaning blade damage.
However, even such conventional photoreceptors are not necessarily sufficient in electrophotographic characteristics and durability, particularly when they are used in combination with a charger of the contact-charging system (contact charger) or a cleaning apparatus, such as a cleaning blade. Further, when a photoreceptor is used in combination with a contact charger and a toner obtained by chemical polymerization (polymerization toner), image quality may be deteriorated due to a surface of the photoreceptor being stained with a discharge product produced in contact charging or the polymerization toner remaining after a transfer step. Still further, the use of a cleaning blade to remove discharge product or remaining toner from the surface of the photoreceptor involves friction and abrasion between the surface of the photoreceptor and the cleaning blade, which tends to damage the surface of the photoreceptor, breaks the cleaning blade or turns up the cleaning blade. As a result of this repetitive cycling, the outermost layer of the photoreceptor experiences a high degree of frictional contact with other machine subsystem components used to clean and/or prepare the photoreceptor for imaging during each cycle. When repeatedly subjected to cyclic mechanical interactions against the machine subsystem components, photoreceptor belts can experience severe frictional wear at the outermost organic photoreceptor layer surface that can greatly reduce the useful life of the photoreceptor. Ultimately, the resulting wear impairs photoreceptor performance and thus image quality. Below are a number of prior art patents and/or publications that discuss the above concepts.
U.S. Patent Publication No. 20090169237 to Shouno et al. discloses a cleaning roller for cleaning a charging roller in an image forming apparatus. The cleaning roller is in contact with an outer peripheral surface of the charging roller to remove foreign materials attached to the outer peripheral surface.
U.S. Pat. No. 6,381,432 to Hattori discloses a power supply roller, which rotates while contacting the surface of the charging roller, and applies a bias to the charging roller for charging a surface of the photoconductive drum uniformly. Brushes may be provided on the surface of the power supply roller. A member may also be supplied for removing toner and sheet particles adhering to the surface of the charging roller and the power supply roller.
U.S. Patent Publication No. 2004019986 discloses a contact cleaning roller which may be axially flexed to conform to a non-planar substrate for removing particles therefrom. A flexible shaft is covered with a high-tack sleeve comprising polyurethane, silicone, adhesive tape, or any other similar high-tack material. The shaft is rotatably suspended at either end in bearings in a frame, allowing the roller to conform to a non-planar substrate surface requiring cleaning.
U.S. Pat. No. 7,515,846 to Miyagi disclose a cleaning device that cleans a charging roller, which charges the outer circumferential surface of a photoconductive drum. The cleaning device has a rotary shaft that rotates in contact with the outer circumferential surface of the charging roller and cleans the outer circumferential surface of the charging roller by brushing. The rotational driving unit rotates the cleaning member. A thrust driving unit reciprocates the cleaning member along the rotary axis of the charging roller while holding the cleaning member in sliding contact with the outer circumferential surface of the charging roller.
U.S. Pat. No. 8,064,791 to Imaizumi discloses a charging device which has a rotatable charging member that electrically charges a photosensitive member. A brush, which rotates along a rotational direction of the charging member by contacting the charging member to receive a force, includes fiber for cleaning the charging member. The fibers have been subjected to a fiber-tilting treatment so that the fibers are tilted in a direction counterdirectionally with a rotation direction of the brush.
U.S. Pat. No. 8,180,256 to Komatsu discloses an image forming apparatus including a photosensitive member, a developing device, a transferring device, a first brush and a second brush. The first brush is downstream of the transfer position and upstream of the photosensitive member charging position. The second brush is downstream of the toner charging position and upstream of the photosensitive member charging position. The first brush is supplied with a charging bias having a polarity opposite to a regular charge polarity of the toner. The second brush is supplied with a charging bias having a same polarity as the regular charge polarity.
U.S. Pat. Nos. 4,435,074, 7,881,651, and US 20100189461 describe a method to use lubricant application brush to apply fine solid powder to PIR surface to lubricate cleaning blade. US 20100189461, US 20110123239, U.S. Pat. No. 7,725,069 describe strategies to extend lifetime of brush applicator.
An improved electrophotographic imaging member has been developed that comprises a very thin outer layer on the imaging member surface that comprises functional materials that act as a lubricant and or a barrier against moisture and/or surface contaminants. The outer layer imparts improved xerographic performance to imaging members incorporating such an outer layer, such as improved wear resistance, low friction, and reduced image defects due to deletion in high humidity conditions. A surface control method has been developed that involves the continuous delivery of a liquid functional material, such as paraffin oil, to the surface of an electrophotographic imaging member through an oil-impregnated delivery roll in direct contact with the BCR (Ser. No. 13/192,215). An improved electrophotographic imaging member comprises a very thin outer layer on the imaging member surface that includes functional materials that act as a lubricant and or a barrier against moisture and/or surface contaminants. The outer layer imparts improved xerographic performance to imaging members incorporating such an outer layer, such as improved wear resistance, low friction, and reduced image defects due to deletion in high humidity conditions.
Illustratively, US Patent Publication No. 20120201585, and U.S. patent application Ser. Nos. 13/192,215, 13/192,252, and 13/279,981, 13/286,905, 13/326,414 describe this improved method of applying, via a delivery roller, an ultra-thin layer of functional materials such as paraffin oil through self-diffusion on ultra-low PIR surface to suppress A-zone deletion and high-torque.
In these embodiments, the delivery roll delivers the functional materials to the outer layer of an imaging surface. As used herein, “functional material” is a material that provides maintenance of desired photoreceptor function. For example, the functional material may be one that is continuously applied onto the photoreceptor surface through direct contact transfer and which can maintain the desired function(s) of the photoreceptor by providing continued lubrication and surface protection. Lubrication of the photoreceptor surface improves interaction with other components in a xerographic system, such as for example, the blade cleaner to reduce torque and blade damage. By maintaining a thin layer of surface material on the photoreceptor, the functional material also provides surface protection to prevent image deletion in, for example, a humid environment such as A-zone.
The paraffin oil as applied over the photoreceptor surface alleviates the chattering of blade and reduces toner contamination on the BCR. However, in practice relying only on this improvement in the delivery roll does not completely address the contamination issue, i.e., there is additive accumulation on BCR during longer-time cycling. Furthermore, additives also start to build up on the delivery roll surface to block effective diffusion of oil from the roll body, which shortens the lifetime of the delivery roll.
Accordingly, a need exists for a new apparatus that extends the lifetimes of the BCR, the photoreceptor, the cleaning mechanism and the delivery roller.